This is a multicenter randomized double blind placebo controlled trial to assess the effectiveness of LJP394 in patients with lupus kidney disease. The primary objective of the study is to determine whether LJP394 is effective in preventing renal flare in patients with a history of lupus kidney disease. Specific aims are as follows: 1)To determine whether LJP 394 is more effective than placebo in reducing anti-dsDNA antibodies in patients with SLE. 2)To determine whether LJP 394 is more effective than placebo in reducing signs and symptons of active SLE as evaluated by the SLEDAI and/or BILAG, SLE Damage Index and the SF-36tm. 3)To determine whether patients treated with LJP 394 require less treatment with cyclophosphamide and prednisone than patients treated with placebo.